Isosbestic point

An isosbestic point is a specific wavelength in a spectroscopic measurement where the absorbance (or transmittance) of the light remains constant, regardless of the concentration of the absorbing species involved in a chemical equilibrium. This phenomenon often occurs in systems where two or more species are interconverting, such as in acid-base reactions, conformational changes, or the binding of ligands to a receptor. In a typical situation involving a chemical equilibrium between two forms (e.g.